/*
 * Copyright:  2018 smarabbit studio.
 *
 *  Licensed under the Confluent Community License; you may not use this file
 *  except in compliance with the License.  You may obtain a copy of the License at
 *
 *  http://www.confluent.io/confluent-community-license
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OF ANY KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations under the License.
 *
 *  @作   者： 黄开晖 (117227773@qq.com)
 *  @日   期:  2019年1月7日
 */

package com.massyframework.beanskin.springboot.beancontext.provider;


import java.io.IOException;
import java.util.Map;
import java.util.Optional;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.web.context.ConfigurableWebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;

import com.massyframework.beanskin.assembly.Assembly;
import com.massyframework.beanskin.assembly.AssemblyContextDelegate;
import com.massyframework.beanskin.assembly.handling.ActivationHandler;
import com.massyframework.beanskin.assembly.handling.EnvironmentHandler;
import com.massyframework.beanskin.assembly.handling.HandlerRegistration;
import com.massyframework.beanskin.assembly.handling.ReadyingException;
import com.massyframework.beanskin.assembly.handling.ReadyingHandler;
import com.massyframework.beanskin.service.ServicePropertiesBuilder;
import com.massyframework.beanskin.service.ServiceRegistration;
import com.massyframework.beanskin.service.ServiceRegistry;
import com.massyframework.beanskin.service.ServiceRepository;
import com.massyframework.beanskin.springboot.beancontext.DependencyServiceBeanDefinitionRegistryPostProcessor;
import com.massyframework.beanskin.springboot.beancontext.DependencyServiceInitializer;
import com.massyframework.beanskin.springboot.beancontext.SpringBeanContextAdapter;
import com.massyframework.beanskin.springboot.beancontext.WebApplicationContextFactory;
import com.massyframework.beanskin.web.utils.ServletRegistrationUtils;

/**
 * 提供DispatcherServlet的装配件上下文处理
 */
final class SpringServletHandler extends DependencyServiceBeanDefinitionRegistryPostProcessor
        implements EnvironmentHandler, ReadyingHandler, ActivationHandler {

    private volatile boolean runAtJ2EE = true;
    private volatile ServiceRegistration<Servlet> servletRegistration;
    private volatile HandlerRegistration<AssemblyContextDelegate<SpringBeanContextAdapter>> contextRegistration;

    private volatile ServletConfig config;
    private volatile DispatcherServlet servlet;

    /**
     * 构造方法
     */
    public SpringServletHandler() {
    }

    /**
     * 初始化
     *
     * @throws Exception 发生非预期的例外
     */
    @Override
    protected void init() throws Exception {
        super.init();
        final Assembly assembly = this.getAssociatedAssembly();
        ServiceRepository repository = this.getServiceRepository(assembly);

        Optional<ServletContext> optional = repository.findService(ServletContext.class);
        ServletException ex = optional.map( context -> {
            this.runAtJ2EE = true;
            try {
                ServletRegistrationUtils.createServletRegistration(
                        context,
                        assembly,
                        null,
                        "true");
            }catch(ServletException e){
                return e;
            }
            return null;
        }).orElse(null);

        if (ex != null){
            throw ex;
        }
    }

    /* (non-Javadoc)
     * @see com.massyframework.assembly.spi.ReadyingHandler#readying()
     */
    @Override
    public synchronized void readying() throws ReadyingException {
        if (!this.runAtJ2EE) {
            return;
        }

        this.exportService();
    }

    /**
     * 输出服务
     */
    protected synchronized void exportService() {
        if (this.servletRegistration == null) {
        	Assembly assembly = this.getAssociatedAssembly();
            ServiceRepository repository = this.getServiceRepository(assembly);
            ServiceRegistry registry = repository.getServiceRegistry();

            Bridge servlet = new Bridge();
            Map<String, Object> props =
                    ServicePropertiesBuilder.newInstance()
                        .name(assembly.getConfig().getParameter("servlet.name"))
                        .build();

            this.servletRegistration =
                    registry.register(Servlet.class, servlet , props);
        }
    }

    /* (non-Javadoc)
     * @see com.massyframework.assembly.spi.ReadyingHandler#unreadyed()
     */
    @Override
    public void unreadyed() throws ReadyingException {
        this.unexportService();
    }

    /**
     * 撤销服务输出
     */
    protected synchronized void unexportService() {
        if (this.servletRegistration != null){
            this.servletRegistration.unregister();
            this.servletRegistration = null;
        }
    }

    /**
     * 在Web场景下注册的组件是否已准备就绪？<br>
     * Servlet的实例化要视注册时的选项，如果是首次请求时才实例化，那在发起首次请求前，本方法只能返回<code>false</code>
     *
     * @return {@link boolean},返回<code>true</code>表示已就绪，否则返回<code>false</code>
     */
    @Override
    public boolean isReady() {
        if (!this.runAtJ2EE) {
            return false;
        }

        return this.config != null;
    }

    /* (non-Javadoc)
     * @see com.massyframework.assembly.spi.ActivationHandler#doStarting()
     */
    @Override
    public synchronized void doStarting() throws Exception {
        if (this.contextRegistration == null) {

        	Assembly assembly = this.getAssociatedAssembly();
            try {
                WebApplicationContextFactory factory =
                        new WebApplicationContextFactory();
                DependencyServiceInitializer<ConfigurableWebApplicationContext> depenedencyInitializer =
                		new DependencyServiceInitializer<>(this);

                ConfigurableWebApplicationContext context =
                        factory.createApplicationContext(assembly,
                        		depenedencyInitializer);
                SpringBeanContextAdapter adapter =
                        new SpringBeanContextAdapter(context);
                AssemblyContextDelegate<SpringBeanContextAdapter> delegate =
                		new AssemblyContextDelegate<SpringBeanContextAdapter>(adapter);
                delegate.init(this.getLifecycleManager());
                this.setAssemblyContext(delegate);
                
                this.servlet = new DispatcherServlet(context);
                servlet.init(this.config);
				
                this.contextRegistration =
                        this.getLifecycleManager()
                            .register(delegate);

            }catch(Exception e) {
                throw e;
            }
        }
    }

    /* (non-Javadoc)
     * @see com.massyframework.assembly.spi.ActivationHandler#doStopped()
     */
    @Override
    public synchronized void doStopped() throws Exception {
        if (this.contextRegistration != null) {
            AssemblyContextDelegate<SpringBeanContextAdapter> context =
                    this.contextRegistration.getHandler();
            this.contextRegistration.unregister();
            this.contextRegistration = null;

            try {
            	context.getBeanContext().getApplicationContext().close();
            }finally {
	            this.servlet.destroy();
	            this.setAssemblyContext(null);
	            this.servlet = null;
            }
        }
    }

    protected void doService(ServletRequest req, ServletResponse res) throws ServletException, IOException {
        Servlet dispatcherServlet = this.servlet;
        if (dispatcherServlet != null) {
            dispatcherServlet.service(req, res);
        }
    }

    /**
     * 根据<code>assembly</code>获取{@link Assembly}
     * @param assembly {@link ServiceExportableModule}, 装配件
     * @return {@link ServiceRepository}
     */
    protected ServiceRepository getServiceRepository(Assembly assembly){
        return ServiceRepository.retrieveFrom(assembly);
    }

    /**
     * ServletBridge在DelegateServlet和DispatcherServletEx之间的连接桥
     */
    private class Bridge implements Servlet {

        @Override
        public void init(ServletConfig config) throws ServletException {
            SpringServletHandler.this.config = config;
            try {
                SpringServletHandler.this.getLifecycleManager().start();
            } catch (Exception e) {
                logError(e.getMessage(), e);
                throw new ServletException(e.getMessage(), e);
            }
        }


        @Override
        public ServletConfig getServletConfig() {
            return config;
        }

        @Override
        public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
            doService(req, res);
        }

        @Override
        public String getServletInfo() {
            return null;
        }

        @Override
        public void destroy() {
            try {
                SpringServletHandler.this.getLifecycleManager().stop();
            } catch (Exception e) {
                logError(e.getMessage(), e);
            }
        }
    }
    
}

